Generally, the term vacuum pump refers to a device that discharges air from a certain space using high-speed compressed air in a vacuum transfer system. Among the various types of vacuum pump, a so-called “inline vacuum pump” refers to a vacuum pump that is configured such that a compressed-air supply line and an exhaust line are arranged in line with each other. This inline vacuum pump is very advantageous in terms of the design of the transfer system, because it does not require an additional pumping means. Examples of an inline vacuum pump are disclosed in U.S. Pat. No. 7,222,901 and Korean Patent No. 817254.
Referring to FIG. 1, the vacuum pump according to U.S. Pat. No. 7,222,901 includes a cylindrical housing 1, an ejector nozzle 2 which is mounted to an inner wall of the housing 1 in such a way as to be in close contact therewith, and a vacuum gripper 3 which is connected to a nozzle intake 6 of the housing 1. Further, an outlet 5 is formed at a predetermined position of the housing 1. Particularly, the nozzle 2 is delicately designed in the form of a double pipe that is bent and branched at an end thereof. An inner pipe 2a extends from an inlet 4 provided on one end of the pump to the outlet 5, while an outer pipe 2b extends from the intake 6 provided on the other end of the pump to the inlet 4 of the inner pipe.
In such a configuration, when the compressed air introduced at high speed is discharged via the inner pipe 2a, internal air of the gripper 3 moves along a gap between the inner pipe 2a and the outer pipe 2b and then is put into the inlet 4, so that the internal air is discharged along with the compressed air. During the exhaust process, a vacuum is created in the gripper 3, thus allowing an object to be gripped and transferred.
However, the conventional pump is problematic in that it is complicated and difficult to design, arrange and implement the components including the nozzle 2 that is delicately designed in structure. Moreover, since the universal nozzle or ejector is never applied to the pump, it is difficult to use the pump in practice.
Referring to FIG. 2, the vacuum pump according to Korean Patent No. 817254 includes a fixed pipe 7 that is secured to an additional structure, a cylindrical slider 8 that passes through the fixed pipe 7 and is arranged to be movable up and down, and a vacuum pump portion 9 that is mounted to an interior of the slider 8 in such a way as to not be in contact therewith. Further, an outlet 10 is formed at a predetermined position of the slider 8. Particularly, the slider 8 is closed at a gripper-side end 11. Around the gripper-side end, an intake passage 12 extending between the gripper and the interior of the slider 8 and a discharge passage 13 extending between the vacuum pump portion 9 and the outlet 10 are designed and processed. Here, an outlet-side end of the vacuum pump portion 9 is fitted into and connected to an entrance of the discharge passage 13.
In this configuration, when compressed air introduced at high speed passes through the vacuum pump 9 and is discharged, the internal air of the gripper flows along the intake passage 12 into the slider 8, and then is introduced into the vacuum pump portion 9 via through holes 14 to be discharged along with the compressed air. During the exhaust process, a vacuum is created in the gripper, thus allowing an object to be gripped and transferred.
However, the conventional pump is also problematic in that it is complicated and difficult to design and implement the components including the intake passage 12 and the discharge passage 13, in terms of structure. The pump also has a problem in terms of function; as the vacuum pump portion 9 moves up and down along with the slider 8, it is unstable in creating and maintaining a vacuum. Meanwhile, since the end of the vacuum pump portion 9 should be air-tightly coupled with the discharge passage 13, there is a limit in selecting a size of the vacuum pump portion, especially a length thereof.